Electric fuse



J. scHURMANN ELECTRIC FUSE Filed Nov. .2l 1926 Dec. 18, 1928.

Patented Dec. 18, 1928.

l 1,695,825! UNITED STATES 4PATENT OFFICE.

JULIUS SCHRMANN, 0F BERLIN-ZEHLE'NDORF, GERMANY.

ELECTRIC FUSE.

Application led November 2, 1926, Serial No. 145,792, and in Germany February 24, 1925.

into an easily handled article or fuse body,

but also to secure this fuse body in the fuse casing or in the detonator shelL-according to the type of fuse-and also to seal the fuse casing.

The substances heretofore used almost exclusively for this purpose consisted either' mainly of sulphur, the so-called sulphur-cements, or even of pure sulphur, these substances being preferred because they are convenient to handle .in the factory and dielectric. but a draw-back to the use of substances of this kind is that, under unfavourable conditions, they may inflame when the fuse is fired and when spread about in burning state they may ignite gas. The tendency in modern mining practice is to increase safety as much as possible.

It is therefore one of the objects of the present invention to reduce the igniting action by the use of non-inflammable or non-combustible substances in electric fuses, for those parts forwhich a plastic substance, which Will subsequently harden, is usually employed.

The invention also contemplates the use, for this purpose, of certain chemical compounds either alone or mixed with one another or with iilling substances. The invention also contemplates the combination of the noninammable substances with other non-inflammable parts of the fuse, in particular With a non-inflammable insulation for the fuse wires, which insulation may, for exam'- ple, consist of asbestos or cotton or paper saturated with certain chemicals, which make these materials non-inflammable.

The non-inflammable plastic hardening substances according to the present invention. may consist, for example, of a mastic of cement or of plaster of Paris or of litharge mixed with Water-glass, oil, glycerine or water or any tWo or more of these substances; the litharge may be Wholly or partly replaced by precipitated chalk or whitening. The noninammable plastic hardening compound may alternatively consist of a casein cement or artiiicial substances derived from acetyl-cellulose or similar incombustible substances which This substance is largely employed y soluble in Water and have a melting point between and 140 C. These substances may be employed either alone or admixed with one anotherl or With suitable filling substances. The highly brolninated and highly fluorinated hydrocarbon compounds are especially' suitable, particularly such compounds for instance as:

' Degrees Tetrachlorbenzol-melting point 137 138 Trich1orpheno1me1ting point 67 68 Triehloraniline-melting point 67 5- 96 Tribromophenol--meltng pont 95 Tribromaniline-melting point 11 Highly chlorinated paraffin and others.

Inorganic filling materials may be added to the compound, such for example as precipitated chalk or Whitening, talc, or asbestos powder. The halogen derivatives of the hydrocarbons may also be mixed with organic substances, such as carnauba Wax, Montan Wax, eumaron resin and bakelite, thereby producing mixtures ranging from those difficult to ignite to non-inflammable substances which can however be easily moulded or cast.

As an example of the present invention, 100 parts of tribromoph-enol melted at 100 C. to 120. C. may be mixed with 25 parts of tale and used as the plastic non-inflammable compound,

The chief advantage of the halogen derivatives of the hydrocarbons is their Waterproof quality.

By a suitable choice of the constituents of the mass and the method of manufacturing the same, the rate of hardening of the plastic mass can be determined according to requirements` and also the hardnessor brittleness aft-er hardening may be kept within desired limits.

So far as the materials are of a porous or hygroseopic nature, this property can be overcome by the mixing of the materials with yshellac or other resins, or by the application of a coating of varnish or by floating a Waterproof substance over the mass, these additions or coatings being used however 1n such small quantities as not to create infiammability.

In the accompanying drawings illust-rating y certain embodiments of the invention, by way of example,

Fig. 1 is a sectional elevation of a fuse of the match-head type having a detonator-or blasting cap-combined therewith.

Figs. 2 and 3 are similar views of a fuse of the match-head type designed to receive a detonator.

Fig. 4 is a similar View of a use with a loose priming charge, having a detonator combined therewith.

In Fig. 1, the numeral 1 designates a metal shell closed at one end and partly filled with an explosive charge 2. The fuse proper 3 lits tightly within ,the shell 1 and consists of a small strip 4 of insulating and preferably non-inlammable material, such as impregnated cardboard, to which are attached conducting coatings 5 and 5', say of tinfoil or nickel foil, which are connected by a tine wire. Around the wire and lower ends of the metal foil is a readily ignitible composition which is formed into a match-head (3. The metal foil coatings 5 and 5 are soldered at 10 and to the free or non-insulated ends 7 and 7 of the fuse wires 9 and 9 which are covered by an insulated covering 8 and 8 which is preferably non-inflammable.. This fuse proper is held in its position in a tube 12 by a non-inflammable filling 11, for example of casein cement or trichlornaphtaline. Tube 12 tightly fits the shell 1 and is preferably rendered reproof. The lower end of the tube 12 projects just beyond the match-head G so that the fuse proper 3 can be pressed down on to the charge 2 without danger and so that a sufficient distance is maintained between the match-head 6 and the explosive charge to obtain effective action. The shell 1 projects above the tube 12 so as to leave a. hollow space which is filled up to the top with a non-combustible mass 13 which may likewise consist of casein cement or any of the substances already mentioned, such as highly chlorinated hydrocarbons. The outer end of the mass 13 and shell 1 is if desired coated with a layer of waterproof varnish 14. A rim 15 on the shell 1 serves to more securely hold the mass 18 in the shell.

In Fig. 2, 16 is a metal tubel open at both ends and designed to receive a detonator. In this example, the fuse proper 17. which is of the same construction as that of Fig. 1, is secured in a non-inflammable mass 18, for eX- ample, of tribromophenol. In this case, a circula-r indentation 19 assists in holding the mass 18 in the tube 16.

In Fig. 3, a similar fuse member 17 is secured in the narrower end of a taperin tube 2O of pasteboard, preferably rendere fireproof by suitable impregnation. The fuse member 17 is secured in the shell by a noninammable mass 21 which may for example consist of an acetyl-cellulose mass. The shell is adapted to receive a detonator.

In Fig. Il, 22 is a metal shell ofa detonator. The fuse proper 23 here consists of two insulated fusc wires 24 and 21 rigidly united at their ends by a cylindrical block 25 of a noninflammable hardening mass, e. g. cement or the like. The bare or non-insulated ends of the wires project from the block 25 and are connected by a tine wire bridge 26. The block 25 seals one end of a tube 27 which is closed at its other end and is preferably made of non-inflammable material, lilled with the loose priming charge 28. That part of the shell 22 which projects beyond the block 25 is filled with a non-inflammable hardening mass 29 which may be similar to that of the block 25 or of any other suitable non-inflammable composition.

In the examples, the use of the invention has been described for fuses having non-in flammable shells and insulation, but the object of the invention, which is tov reduce the danger of gas ignition by burning parts of the fuse, can also be attained if the non-inflammable substances are used in conjunction with inflammable fuse parts.

The arrangement of the shell, tubes, wires and leads is not an essential feature of the present invention, nor is it intended that the invention be limited to the examples illustrated.

I claim- In an electric fuse of the type described, the combination with a non-combustible mass practically enclosing the inflammable fuse parts, of non-inflammable, non-combustible insulation enclosing the fuse-wires, a nonintlammable st rip leading to and supporting the ignitible initial charge, conducting coatings covering the sides of said strip, and a conductor between said conducting coatings.

In testimony whereof I aiix my signature.

JULIUs SGHRMANN. 

